THE BIOLOGY OF THE ALDER FLEA-BEETLE. 273 



COPULATION. 



The male and female remain in copulation several hours. 

 The writer has never observed them to pair more than once, but 

 it is probable that they do, since this is quite characteristic of 

 related species. 



NUMBER OF EGGS DEPOSITED BY A SINGLE FEMALE. 



The writer has very little data as to the number of eggs 

 which one female may deposit. None of the females which he 

 has isolated after pairing deposited more than 35 eggs. But 

 related species may deposit as high as 500 eggs per female, and 

 doubtless 35 is far too low even to approximate the number of 

 eggs which one female bimarginata can deposit. They usually 

 begin to oviposit within a few days after pairing. 



NATURAL ENEMIES. 

 FUNGOUS ENEMIES. 



Both in the laboratory and in the field, larvae, prepupae, 

 pupae, and adults are very susceptible to the attacks of Sporo- 

 trichum globnlifcrum Speng. if the conditions are right for 

 infection. The writer does not doubt that this fungus played 

 an important part in checking the outbreak of the alder flea- 

 beetle, since it was abundant both in 1914 and 1915. While 

 probably the fungus was not the only agent in the extermination 

 of this species, nevertheless the extreme abundance of these 

 insects offered ideal conditions for fungus to work, and doubt- 

 less great numbers of Altica bimarginata were destroyed in this 

 way. Dr. Roland Thaxter of Harvard University kindly deter- 

 mined the species of fungus for the writer. 



The pupae are quite subject to a wilt-disease, probably 

 bacterial in its nature, but the writer has made no attempt to 

 isolate the causative organism. 



INSECT PARASITES. 



An interesting parasite was bred from the adult beetles in 

 the summer of 1915, a dipterous insect of the family Tachinidae, 

 which was determined by Mr. C. W. Johnson of the Boston 



